Function with_lock 

pub fn with_lock<T, E, F>(f: F) -> Result<T, E>
where
    F: FnOnce() -> Result<T, E>,
    E: From<LockError>,

Acquires an exclusive flock on the registry-cache lock file for the duration of f. The lock file is created on first use. Released when f returns (including via panic-unwind, since the underlying file descriptor is closed by Drop).

Use this around every operation that touches refs, the PID file, the config file, or the zot process state. Generic over the caller’s error type E (which must be constructible from LockError) so callers can propagate their own error variants from f without a boxed catch-all.